1. Field of the Invention
This invention generally relates to a bicycle force sensing device. More specifically, the present invention relates to a bicycle force sensing device for sensing a pedaling force being applied to a crank axle.
2. Background Information
Bicycles are sometimes equipped with a force sensor for detecting a force acting on the bicycle crank axle. For example, in U.S. Pat. No. 7,516,677 (assigned to Shimano Inc.), a cylindrical torsion-detecting sleeve member (force sensor unit) is provided on a crank axle for detecting a torque applied to the crank axle. Another example of a force sensor for detecting force acting on the bicycle crank axle is disclosed in EP Patent Publication No. 1,361,822. In this patent publication, sensors are positioned between a radial inner surface of the bottom bracket tube and a radially extending outer surface of an annular member that surrounds one of the crank axle bearings. With these arrangements, the strain sensors have to be orientated in a prescribed orientation in order to accurately measure the force acting on the bicycle crank axle. Thus, with these arrangements, a main body is fixed to an adaptor by bolts, and then a user fixes the adaptor to a bicycle bottom bracket and adjusts the orientation of the main body after adaptor has been fixed to the bicycle bottom bracket.